Our goal is to explore the nature and role of endogenous electrical currents controlling the growth and degrowth of nerve growth cones. We expect to meausre the currents which may traverse such growth cones using our newly developed vibrating probe; first using explants or short term cell cultures of chick dorsal root ganglia grown in relatively physidogical media; then with other media and other preparations in an effort to find those current components most closely correlated with growth or degrowth. We then plan to explore the specific ions which carry these currents across the cone's plasma membrane and the net conductance of this membrane; both the immediate electrical current changes in response to particular ion changes in the media, as well as radioautography after exposure to media bearing tracer ions, should yield such data. Finally, guided by these findings, galvanotropic studies will be planned to explore to what degree the endogenous currents act back to control cone extension and retraction.